A scrub cleaning method has been known as a method for cleaning a substrate such as, e.g., a silicon wafer or a compound semiconductor wafer. The scrub cleaning method removes foreign substances attached to the front surface of a substrate by bringing a rotating brush or a rotating sponge into contact with the front surface of a substrate.
A substrate cleaning apparatus employing the scrub cleaning method is provided with a cleaning body such as, e.g., a brush at the lower end of a shaft which is rotated by a motor and moved up and down by an air cylinder. The contact force of the cleaning body on a substrate is adjusted by adjusting buoyancy generated by the air cylinder. A conventional substrate cleaning apparatus is provided with a sensor configured to detect total weight of, for example, the cleaning body and the shaft. A desired contact force may be obtained by generating the buoyancy of the air cylinder by the difference of a pre-set desired contact pressure and an output from the sensor.
Meanwhile, in the conventional substrate cleaning apparatus, a motor for rotating the shaft of the cleaning body is provided separately from the shaft and the rotation of the motor is transferred to the shaft by a transfer belt extended between a pulley attached to an output shaft of the motor and a pulley attached to the shaft, thereby rotating the cleaning body. See, e.g., Japanese Patent Laid-Open Publication No. H7-307321.